After some significant trial and error I was able to get my GTI through Maryland state emissions. I'm going to post my setup here so it can hopefully help someone in the future because I know this is a frustrating issue.
2011 CBFA GTI
CTS K04
ECS Tuning Downpipe w/200 cell metallic cat
Vibrant J spacer (Vibrant p/n 11619) with the medium insert on the post cat sensor. Spacer points toward the front of the car (pic below).
Tune from Stratified - STOCK with codes U1030 & U102F toggled OFF to prevent codes thrown by faulty G611 Radiator Identification Sensor
I had two major issues to overcome:
-The P0420 code caused by my aftermarket downpipe
-The U1030 & U102F codes caused by a faulty G611 Radiator Identification Sensor
This setup allowed all readiness monitors to set after driving around gently for a few days without going into boost. A previous attempt used this same hardware setup but the tune was my current K04 tune with U1030 & U102F toggled OFF. For some reason the Oxygen Sensor monitor would not pass. Switching to the Cobb stock tune or Cobb Stage 1 tune allowed all readiness monitors to set but I still had the CEL for the G611 sensor. Jared to the rescue with the final version of my "emissions tune" which was just a stock tune with U1030 & U102F toggled off.
Glad to have that behind me so I can put the K04 tune back on and have fun.
I purchased a G611 sensor for a Mercedes just in case I couldn't get the tuning to work. You just need to solder the 4 wires to the VW connector (they're color coded so dummy proof, I can provide a link on this forum to someone who successfully made this sensor work). The sensor is for sale if anyone is interested. They're typically quite expensive and difficult to obtain but I snagged one new on eBay. Just want to make some of my money back so it's for sale and I'll make someone a good deal to help them get through emissions or eliminate a pesky CEL.